Dynamically controllable patient fluid control device

ABSTRACT

A fluid control device includes an interface to a remote fluid monitoring sensor that detects fluid flow in a patient. In some embodiments, a processor within the fluid delivery device is programmed to adjust the delivery or withdrawal of fluids based on the fluid flow signals provided by the sensor. In some embodiments, the fluid control device can display and/or record fluid flow signals thereby acting as a hemodynamic monitor.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims the benefit of, and priority to, U.S.Provisional Patent Application No. 62/640,903 filed Mar. 9, 2018, whichis herein incorporated by reference in its entirety.

TECHNICAL FIELD

The disclosed technology relates to medical fluid control devices.

SUMMARY

As will be discussed in further detail below, one embodiment of thedisclosed technology relates to a patient fluid control device that isconfigured to receive signals (e.g., Doppler velocimetry, or othersignals derived from an echocardiography interrogation of a vessel) froma sensor that detects fluid flow (e.g. blood flow) in one or more of apatient's vessels. The fluid control device includes one or moreprocessors that are programmed to analyze the fluid flow measurementsand adjust the delivery of fluids based on the detected fluid flow.

In another embodiment, the disclosed technology relates to a fluidcontrol device that removes or recirculates fluid from a patient such asa dialysis machine. The device is configured to receive signals from asensor that detects fluid flow in one or more of a patient's vessels ina static or dynamic (i.e., repeated) manner over the course of aclinical intervention. The device includes a processor that isprogrammed to adjust the removal of fluid from the patient based on thesignals received from the sensor.

In some embodiments, a processor is programmed to compare one or moremeasurements of fluid flow versus an event that should change the fluidflow. Such an event can be the delivery or withdrawal of fluid from thepatient or a physical intervention such as a leg raise,ventilator-delivered breath or the like. Signals from the flow sensorare analyzed by the processor for changes in fluid flow measured beforeand after the event. The processor is programmed to alert the clinicianand/or adjust the delivery or withdrawal of fluid from the patient basedin part on the signal analysis.

In some embodiments, the fluid control device delivers fluids such as anintravenous fluid pump, and in other embodiments, the fluid controldevice withdraws or recirculates fluids such as a dialysis machine. Theterm “fluid control device” is therefore intended to refer to anyprogrammable device that is connectable to a flow sensor and thatdelivers or withdraws fluids from a patient. The devices are connectedvia a wired or wireless communication link to a fluid flow sensor thatmonitors fluid flow (e.g. blood flow) through one or more vessels. Insome embodiments, the sensor is an ultrasound patch sensor that directsultrasound signals into the patient and detects a Doppler shift in thereturn signals detected by the sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a fluid delivery device in accordance withsome embodiments of the disclosed technology;

FIG. 2 illustrates two possible changes occurring in a patient'scomputed velocity time integral (VTI) after a partial delivery of afluid bolus;

FIG. 3 illustrates two possible changes occurring in a patient's venousDoppler signal after a partial delivery of a fluid bolus;

FIG. 4 illustrates possible changes to a peak systolic velocity and anend diastolic velocity and changes of systolic versus diastolic velocitythat are simultaneously measured and used to adjust the delivery of atherapy in accordance with some embodiments of the disclosed technology;and

FIG. 5 illustrates a representative user interface (UI) on a fluidcontrol device that shows fluid flow measurements obtained by a remotefluid flow sensor.

DETAILED DESCRIPTION

FIG. 1 is a block diagram of a system for controlling a fluid controldevice in accordance with some embodiments of the disclosed technology.In some embodiments, the fluid control device is designed to deliverfluids to a patient such as a programmable intravenous pump. In otherembodiments, the fluid control device is designed to withdraw orwithdraw and replace fluids from a patient such as a dialysis machine.In the embodiment shown, a fluid delivery device 50 includes a processor52 that is configured to execute programmed instructions stored in amemory 54. A display 56 provides visual information to an operatorregarding one or more of a rate at which fluids are to be delivered tothe patient, the amount of fluid delivered, the time left until fluiddelivery is complete etc. A user interface 58 such as a number ofbuttons, a keyboard or a touch sensitive screen on the display 56 allowsan operator to turn the machine on/off, enter patient data, change therate of delivery, program a bolus delivery of fluid, program a start orstop time etc. A fluid pump 62 is controllable by the processor 52 todeliver precise quantities of a fluid 64 to a patient 70 at a knownrate.

In conventional fluid delivery devices, programmed quantities of fluidsare delivered at a programmed rate without feedback from the patient 70regarding how the fluids are being received. A fluid delivery device 50according to the disclosed technology includes aninterface/communication port 60 that receives signals from a flow sensor72 that monitors fluid flow or other vessel parameters in the patient70. In one embodiment, the flow sensor 72 detects Doppler signals fromone or more vessels in the patient and returns the Doppler signalsand/or measurements of the detected flow via a wired (e.g. USB, twistedpair, fiber optic, co-axial cable etc.) or wireless (Bluetooth,Bluetooth LE, Wi-Fi, Zigbee, IR etc.) communication link 75 and arereceived at the interface 60. Communication signals received at theinterface 60 are provided to the processor 52. In some embodiments, theinterface/communication port 60 is a physical port into which acorresponding USB plug, twisted pair of cables, co-axial cable or thelike is inserted in order to connect the fluid delivery device to theflow sensor 72. In other embodiments, the interface/communication port60 is an antenna and communication circuitry or an IR receiver etc. thatconverts wireless signals into electronic signals that can be processedby the processor 52.

The signals from the flow sensor 72 are received by the fluid deliverydevice 50 and used to adjust the delivery of fluids to the patient 70.In one embodiment, the flow sensor 72 is a pulsed or continuous waveultrasound device having at least one transmit element and at leastelement that acts as a receive element. In case of pulsed ultrasound,the transmit element and the receive element may be the same. Ultrasoundsignals are periodically or continuously transmitted towards a vesseland the reflected ultrasound signals are detected and processed in orderto detect the Doppler shift due to blood flowing towards or away fromthe sensor 72.

If the communication link 75 has sufficient bandwidth, raw ultrasounddata signals can be transmitted to the fluid delivery device 50 to beprocessed off the flow sensor 72. However, in most embodiments, signalprocessing circuitry and a processor or microcontroller (not shown)within the sensor 72 detect the Doppler signals and a produce adigitized version of the Doppler signals and measurements obtainedtherefrom for transmission via the wired or wireless communication link75 to the fluid delivery device 50. In some embodiments, one suitableflow sensor 72 is described in U.S. patent application Ser. No.15/877,251 filed Jan. 22, 2018 and published as U.S. Patent PublicationNo. US 2018-0353157 A1, which is herein incorporated by reference in itsentirety. In some embodiments, the flow sensor samples the forward andreverse flow Doppler signals to determine their peak values and thecentroid frequency/velocity at each sample point. This information istransmitted wirelessly to the flow control device to allow the flowcontrol device to reproduce the Doppler waveforms and calculate metricsfrom the Doppler information such as Doppler power, VTI (velocity timeintegral), systolic flow time, etc.

In the embodiment described, the flow sensor 72 is a stand-alone devicethat processes the received ultrasound data to determine the Dopplershifts and communicates with the fluid delivery device 50 via thecommunication link 75. In other embodiments, some signal processingcomponents of the flow sensor 72 may be incorporated into the fluiddelivery device 50 and the flow sensor 72 includes the ultrasoundtransmit and receive elements but not all the signal processingcomponents. The fluid delivery device includes some signal processingcomponents necessary to receive either an analog or digitized version ofthe reflected ultrasound signals and determine the Doppler shifts andcompute the metrics therefrom.

As will be appreciated by those skilled in the art, the fluid deliverydevice 50 also includes additional components besides those shown inFIG. 1, which are omitted to avoid obscuring aspects of disclosedtechnology. For example, the fluid delivery device generally includes apower supply and communication circuitry to send signals and/or alarmsto hospital patient monitoring systems.

Doppler signals and/or measurements computed therefrom are received bythe fluid delivery device 50 at the interface 60 and relayed to theprocessor 52 of the fluid delivery device that is programmed tostart/stop/alter the delivery of fluids based on the informationreceived from the flow sensor 72. In some embodiments, the flow sensor72 detects other measurements besides the Doppler shift of blood flowingin the vessels. Vessel sizes can also be detected from returnedultrasound data. When combined with Doppler signals flowing towards oraway from the sensor, estimates of the sizes of different vessels suchas the carotid artery versus the jugular vein can be determined andtransmitted to the fluid delivery device 50.

In some embodiments, the processor or logic circuitry in the fluiddelivery device 50 is configured to perform one or more ofauto-titration of administered intravenous fluids, delivery vasoactivemedications, to perform dialysis and/or to produce fluid/medicationinduced warning signs. The device 50 receives real-time arterial andvenous Doppler waveforms from a patient (via the flow sensor 72described above or other Doppler-based input). As its output, the devicecan provide an indication to an operator to adjust, or can auto-adjust,one or more of: the infusion rate and volume of intravenous fluids aswell as the dose and concentration of vasoactive medications. The fluiddelivery device 50 can also provide a warning alarm if vital signalsindicate a medication/fluid may be causing a problem for the patient(e.g., opioids decreasing respiratory rate, fluids inducing atrialfibrillation etc.).

Intravenous Fluids and Dialysis

In some embodiments, the fluid delivery device 50 is configured toadjust the rate and volume of intravenous fluid based on a quantitativeand/or qualitative change in an arterial and/or venous Doppler waveform.The device 50 may also have a warning system/alarm for clinicians priorto making any change in fluid infusion. The venous and arterial Dopplerwaveforms may be obtained from the external flow sensor 72 or aninternal non-invasive or invasive Doppler detection device.

Methods for assessing fluid responsiveness of the heart from an arterialwaveform include detecting a change in one or more of: peak systolicvelocity, mean velocity, velocity time integral, systolic flow time, enddiastolic velocity, absolute flow, Doppler power, and velocity-powercombinations. The absence of change, or a decrease, in one or more ofthe aforementioned variables in response to a fluid infusion/bolus orother provocative maneuver such as a passive leg raise, change inintra-thoracic pressure, or dialysis can warn the clinician and/or slowor cease infusion of intravenous fluid (or dialysis of fluids)automatically is so programmed. The fluid delivery device 50 may alsohave auto-programmed protocols which infuse a known volume ofintravenous fluid and assess the change in the aforementioned arterialDoppler parameters. From this data, fluid infusion or dialysis can beincreased, slowed or ceased as so programmed by the clinician.

FIG. 2 depicts simple input-measurement-output for the fluid deliverydevice 50. Note that the intervention is not limited to a fluidchallenge but, as above, could also rely upon a leg raise or changes inarterial Doppler based on respiratory variation amongst other stressesplaced upon the heart. This process may be iterative. In the embodimentshown, a clinician programs the fluid delivery, device 50 to administera 1000 ml. fluid bolus. Instead of delivering the entire bolus at onetime, the device 50 is programmed to deliver a partial bolus and comparethe fluid flow measurements pre and post administration. In the exampleshown, the pre-bolus maximum fluid velocity 100 is 100 cm/s. The systemadministers a partial 250 ml. bolus and the post bolus Dopplermeasurements are obtained for comparison. A 100 to 120 cm/s velocityincrease 104 represents a 20% increase in peak systolic velocity [PSV];the y-axis is Doppler velocity; the shaded area is the VTI or velocitytime integral for the Doppler pulse. In the embodiment shown, anincrease in the PSV is detected and the processor 52 of the fluiddelivery device 50 is programmed to deliver the 750 ml. remainder of thebolus. On the other hand, if no increase 106 in the PSV is detected, theprocessor 52 of the fluid delivery device 50 can operate to hold theremainder of the bolus and set an alarm for an operator.

In some embodiments, the processor of the fluid delivery device storesthe pre and post bolus Doppler waveforms in a memory for inclusion intoa patient record or for other purposes.

Methods for assessing fluid responsiveness of the heart from an arterialwaveform also include detecting a change in the morphology of thearterial waveform, for example a Doppler flow time. As described below,changes in waveform morphology in response to vaso-active infusion canbe integrated with on-going assessment of fluid responsiveness followingauto-titration of vaso-active medication.

Methods for warning the clinician and/or slowing or ceasing the infusionof intravenous fluid from a venous waveform may include the qualitativeor quantitative analysis of the venous velocity morphology as a markerof central venous pressure [i.e. CVP]. The venous waveform can alsoinclude relating the diameter of the carotid artery to the diameter ofthe jugular vein as a marker of CVP or by relating surrogates forarterial and jugular diameter as an indication of central venouspressure. The fluid delivery device 50 may also execute auto-programmedprotocols that infuse a known volume of intravenous fluid and assess thechange in the aforementioned venous Doppler parameters. From this data,fluid infusion can be increased, slowed or ceased as so programmed bythe clinician.

FIG. 3 depicts a similar iterative process to FIG. 2, but instead, aqualitative analysis of the venous Doppler waveform is utilized. Wave110 represents the pre-challenge venous Doppler waveform, while waves112 and 114 represent possible post-challenge Doppler waveforms. Notethat the provocation need not be a fluid challenge such as a bolusdelivery but could include a provocative maneuver such as a change inintra-thoracic pressure, ventilator-delivered breath, body position ordialysis. Further, the analysis could include quantitative assessment ofvenous Doppler waveform or other ultrasound-based assessments of thecentral venous pressure. As shown in FIG. 3, S is systolic venous wave,D is diastolic venous wave, a and v are A and V waves, respectively,which are well-known waves in the CVP—the A wave is the first positivedeflection and is the result of the atrial kick while the V wave is thesecond positive deflection—it's peak marks ventricular filling.

In the example shown, a clinician orders a 1000 ml bolus to be given andthe fluid delivery system delivers a partial bolus of 250 ml. Dopplervenous signals obtained before and after the fluid challenge areobtained and compared. If little or no changes to the venous Dopplerwaveform 110 occur, then the fluid delivery device continues to deliverthe rest of the 1000 ml. bolus. On the other hand, evolving (e.g.increasing) A and V waves with a reversed S/D ratio (shown in waveform114) (e.g. the peak diastolic speed now exceeds the peak systolic speed)is highly suggestive of high right heart pressure. In one embodiment,the fluid delivery system suspends the delivery of the remainder of thebolus and/or alerts a clinician. This is but one example of venousDoppler analysis.

If a non-fluid challenge is used, the fluid control device can beprogrammed to produce an instruction on its display or an audiblecommand telling an operator to perform a leg raise etc. In this way, thefluid control device can look for changes in the Doppler signals afterthe instruction is given. In other embodiments, the fluid control devicecan receive signals from a ventilator or other medical device indicatingwhen a therapy is given in order to mark the time to begin looking forchanges in the Doppler signals from the remote sensor.

Vaso-Active Medications

As different states of shock result from different pathologies of theheart and/or vasculature, the correction of shock requires specificselection and titration of vaso-active medication(s). The subtype ofshock may be inferred from a pattern of arterial and/or venous Dopplerwaveform analysis. Therefore, vaso-active selection and titration may bebased on device analysis of Doppler inputs. Consider the example of ashocked patient with a waveform profile as shown in FIG. 4.

FIG. 4 illustrates a hypothetical analysis of simultaneous arterial andvenous waveform velocimetry as inputs for an infusion device to makeautomated changes in intravenous fluids and/or vasoactive medications.Normal arterial and venous Doppler waveforms 120, 124 are included forcomparison [shown in dotted lines]. This is one example of manypotential analyses in the shocked patient.

The arterial Doppler waveform 122 reveals a lower velocity timeintegral—suggesting low stroke volume. This is accompanied by a veryhigh end-diastolic arterial Doppler velocity (EDV)—suggesting lowperipheral arterial resistance. If simultaneous venous Doppler analysisstrongly suggests a high central venous pressure (e.g. waveform 126)—CVP(such as indicated by an increase in the diastolic venous velocitycompared with the systolic venous velocity), it is likely that there issimultaneous cardiac dysfunction based on Guytonian physiology. Thus,fluids would be warned against, slowed or ceased and the fluid deliverydevice can be programmed to suggest a vasoactive medication thatincreases both cardiac output and peripheral vascular resistance or theinfusion dose increased [e.g. epinephrine or to a lesser extentnor-epinephrine], In this state, a vasoactive medication that increasescardiac function and further lowers peripheral vascular resistance [e.g.dobutamine] would be warned against or down-titrated through the fluiddelivery device infusion pump. A similar analysis can be made for othertypes of general shock such as hypovolemic, cardiogenic, obstructive anddistributive and mixed types.

Changes in vaso-active medications may be suggested by the device orautomatically executed based on programmed protocols.

Although the disclosed technology is primarily described with respect toa fluid delivery device such as an intravenous fluid pump, thetechnology is equally useful with other types of fluid managementsystems such as dialysis machines. In this embodiment, the deviceincludes an interface or communication port where Doppler signals (orun-processed ultrasound echo data) are received from a remote sensor andcan be processed and measured by a processor prior to and after theremoval of blood for filtering. Doppler signals or other ultrasoundmeasurements are received from a fluid flow sensor and are analyzed by aprocessor in the device to halt/continue or adjust the rate of fluidwithdrawal and replacement.

By including an interface to receive fluid flow measurements from asensor attached to the patient, the fluid delivery/management device 50become in effect a hemodynamic monitor that can monitor blood flow overperiods of time. Blood flow can be recorded and upper and or lowerlimits can be set to produce alerts should the limits be exceeded. Insome embodiments, the fluid delivery/control device records Dopplerwaveforms during the course of a longer procedure (e.g., dialysis orother) where multiple readings of the Doppler waveforms are plottedagainst each other to identify changes over time.

FIG. 5 shows an exemplary user interface (UI) on an infusion pump whereDoppler waveforms over a number of cardiac cycles are shown on adisplay. In the embodiment shown, the UI displays (% changepost/pre-fluid challenge) 150, the general Doppler waveform 152 andhistograms 156 showing a beat by beat quantification of a Dopplerwaveform parameter. Note this UI could be toggled to zoom/focus ondifferent data visualizations (e.g., just the arterial waveform, justthe venous waveform etc.), and time averaged sampling forpost/pre-analysis is also enabled. The UI is intended to allow theinfusion pump to also function as a hemodynamic monitor.

Measurements from the Doppler waveform such as VTI or peak or centroidvelocities can be calculated and displayed. Similarly, such measurementscan be averaged and displayed over a number of cardiac cycles. Aclinician can perform some fluid challenge and can view how thechallenge affects the detected vascular flow.

In some embodiments, an intravenous pump/monitor, dialysis machine or abedside ultrasound machine receives a measured “calibrated” leftventricular stroke volume (measured invasively or non-invasively) andincludes a processor that is programmed to fit the measured leftventricular stroke volume to simultaneously-obtained carotid Dopplertracings from a flow sensor attached to the patient. The calibration ofthe measured left ventricular stroke volume may be made to fit thecarotid velocity, power, velocity-power and/or metrics derived from theDoppler signals produced by the flow sensor. Thereafter, real-timechanges in left ventricular stroke volume can be tracked byextrapolation from changes in the carotid Doppler signals.

Embodiments of the subject matter and the operations described in thisspecification can be implemented in digital electronic circuitry, or incomputer software, firmware, or hardware, including the structuresdisclosed in this specification and their structural equivalents, or incombinations of one or more of them. Embodiments of the subject matterdescribed in this specification can be implemented as one or morecomputer programs, i.e., one or more modules of computer programinstructions, encoded on computer storage medium for execution by, or tocontrol the operation of, data processing apparatus.

A computer storage medium can be, or can be included in, acomputer-readable storage device, a computer-readable storage substrate,a random or serial access memory array or device, or a combination ofone or more of them. Moreover, while a computer storage medium is not apropagated signal, a computer storage medium can be a source ordestination of computer program instructions encoded in anartificially-generated propagated signal. The computer storage mediumalso can be, or can be included in, one or more separate physicalcomponents or media (e.g., multiple CDs, disks, SSDs, on-chipnon-volatile memory or other storage devices). The operations describedin this specification can be implemented as operations performed by adata processing apparatus on data stored on one or morecomputer-readable storage devices or received from other sources.

The term “processor” encompasses all kinds of apparatus, devices, andmachines for processing data, including by way of example a programmableprocessor, a programmed microcontroller, a computer, a system on a chip,or multiple ones, or combinations, of the foregoing. The apparatus caninclude special purpose logic circuitry, e.g., an FPGA (fieldprogrammable gate array) or an ASIC (application-specific integratedcircuit).

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, declarative orprocedural languages, and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, object, orother unit suitable for use in a computing environment. A computerprogram may, but need not, correspond to a file in a file system. Aprogram can be stored in a portion of a file that holds other programsor data (e.g., one or more scripts stored in a markup languagedocument), in a single file dedicated to the program in question, or inmultiple coordinated files (e.g., files that store one or more modules,sub-programs, or portions of code).

The processes and logic flows described in this specification can beperformed by one or more programmable processors executing one or morecomputer programs to perform actions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application-specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, aprogrammed microcontroller, and any one or more processors of any kindof digital computer. Generally, a processor will receive instructionsand data from a read-only memory or a random access memory or both. Theessential elements of a computer are a processor for performing actionsin accordance with instructions and one or more memory devices forstoring instructions and data. Generally, a computer will also include,or be operatively coupled to receive data from or transfer data to, orboth, one or more mass storage devices for storing data, e.g., solidstate drives SSDs, magnetic, magneto-optical disks, or optical disks.Devices suitable for storing computer program instructions and datainclude all forms of non-volatile memory, media and memory devices,including by way of example semiconductor memory devices, e.g., EPROM,EEPROM, and flash memory devices; magnetic disks, e.g., internal harddisks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROMdisks. The processor and the memory can be supplemented by, orincorporated in, special purpose logic circuitry.

To provide for interaction with a user, embodiments of the subjectmatter described in this specification can include a display device,e.g., an LCD (liquid crystal display), LED (light emitting diode), orOLED (organic light emitting diode) monitor, for displaying informationto the user and a keyboard and a pointing device, such as a touch screenthat can be used to display information and to receive input from auser. Other kinds of devices can be used to provide for interaction witha user as well; for example, feedback provided to the user can be anyform of sensory feedback, e.g., visual feedback, auditory feedback, ortactile feedback; and input from the user can be received in any form,including acoustic, speech, or tactile input. The biosensor or pump mayalso be configured to push information to cellular devices, mobilenetworks or smart devices (e.g., glasses and/or watch).

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from theand scope of the invention. For example, although the embodimentsdescribed are for fluid control devices for use on humans, the disclosedtechnology could also be used with veterinary fluid control devices.Accordingly, the invention is not limited except as by the appendedclaims.

We claim:
 1. A fluid control device, comprising: a processor programmedto execute a number of instructions; a fluid pump that is configured tocontrol fluids under control of the processor; and a communication portthat is configured to receive fluid flow signals from a remotely locatedflow sensor; a memory for storing the fluid flow signals received fromthe remotely located flow sensor; and a display for displaying the fluidflow signals received from the remotely located flow sensor; wherein theprocessor is configured to execute instructions to control the fluidpump based on the fluid flow signals received from the remotely locatedflow sensor; and wherein the fluid flow signals are indications of amaximum arterial and venous flow rates from sampled Doppler waveforms.2. The fluid control device of claim 1, wherein the fluid flow signalsare Doppler signals.
 3. The fluid control device of claim 1, wherein theinstructions cause the processor to: receive an instruction to deliver abolus of fluid to a patient; receive signals indicative of a fluid flowin the patient before delivering the bolus; deliver a portion of thebolus to the patient; receive signals indicative of the fluid flow inthe patient after the portion of the bolus has been delivered; comparethe signals indicative of fluid flow before and after the portion of thebolus was delivered; and deliver a remainder of the bolus based on thecomparison.
 4. The fluid control device of claim 1, wherein the Dopplersignals are derived from arterial and venous blood flow in vessels of apatient.
 5. The fluid control device of claim 1, wherein thecommunication port is configured to receive wireless communicationsindicative of fluid flow in a patient from the remotely located flowsensor.
 6. The fluid control device of claim 1, wherein the processor isprogrammed to compare the fluid flow signals received prior to and aftera challenge designed to change the blood flow in a patient and tocontrol the pump based on the comparison.
 7. The fluid control device ofclaim 6, wherein the processor is programmed to deliver a bolus ofliquid to the patient as a challenge.
 8. The fluid control device ofclaim 6, wherein the processor is programmed to generate an instructionto an operator to administer the challenge to the patient.
 9. The fluidcontrol device of claim 6, wherein the processor is programmed togenerate an alarm based on the comparison.
 10. A fluid control device,comprising: a processor programmed to execute a number of instructions;a fluid pump that is configured to control fluids under control of theprocessor; and a communication port that is configured to receive fluidflow signals from a remotely located flow sensor; a memory for storingthe fluid flow signals received from the remotely located flow sensor;and a display for displaying the fluid flow signals received from theremotely located flow sensor; wherein the processor is configured toexecute instructions to control the fluid pump based on the fluid flowsignals received from the remotely located flow sensor; and wherein theprocessor is programmed to compare the fluid flow signals received priorto and after a challenge designed to change the blood flow in a patientand to control the pump based on the comparison.
 11. The fluid controldevice of claim 10, wherein the processor is programmed to deliver abolus of liquid to the patient as a challenge.
 12. The fluid controldevice of claim 10, wherein the processor is programmed to generate aninstruction to an operator to administer the challenge to the patient.13. The fluid control device of claim 10, wherein the processor isprogrammed to generate an alarm based on the comparison.
 14. The fluidcontrol device of claim 10, wherein the instructions cause the processorto: receive an instruction to deliver a bolus of fluid to a patient;receive signals indicative of a fluid flow in the patient beforedelivering the bolus; deliver a portion of the bolus to the patient;receive signals indicative of the fluid flow in the patient after theportion of the bolus has been delivered; compare the signals indicativeof fluid flow before and after the portion of the bolus was delivered;and deliver a remainder of the bolus based on the comparison.
 15. Thefluid control device of claim 10, wherein Doppler signals are derivedfrom arterial and venous blood flow in vessels of a patient.
 16. Thefluid control device of claim 10, wherein the communication port isconfigured to receive wireless communications indicative of fluid flowin a patient from the remotely located flow sensor.